The effective intestinal permeability (Peff) of cyclosporin A (CsA) and interindividual variability of CsA Peff will be determined in the upper jejunum of healthy volunteers by using a regional intestinal perfusion technique. The amount of P-glycoprotein and Cytochrome P450 IIIA4 (CYP3A4) in the intestine will be measured to examine the potential contribution of intestinal secretion and metabolism to the Peff of CsA.